How is ethanol manufactured industrially?

Ethanol is industrially manufactured through the process of fermentation and distillation, primarily using yeast and sugar.

In more detail, the production of ethanol begins with the process of fermentation. This is a natural process where yeast, a type of fungus, is added to a solution of sugar. The yeast consumes the sugar and as a result, produces ethanol and carbon dioxide. This process is anaerobic, meaning it occurs in the absence of oxygen. The chemical equation for this reaction is: C6H12O6 (glucose) → 2C2H5OH (ethanol) + 2CO2 (carbon dioxide).

However, the fermentation process only produces a solution with around 15% ethanol because the yeast cells die when the concentration of ethanol becomes too high. To increase the concentration of ethanol, the solution is heated in a process called distillation. As ethanol has a lower boiling point than water (78.37°C compared to 100°C), it evaporates first when the solution is heated. The ethanol vapour is then cooled and condensed to form a liquid with a much higher concentration of ethanol.

In industry, this process is carried out in large fermentation vats and distillation columns. The sugar used in the process often comes from crops such as sugar cane or corn. However, this has led to some controversy as these crops could be used as food. As a result, there is ongoing research into using other sources of sugar, such as waste plant material.

It's also worth noting that ethanol can be produced synthetically from ethene and steam, in a process known as hydration. However, this method requires a high temperature and a catalyst, and ethene is derived from crude oil, a non-renewable resource. Therefore, the fermentation and distillation method is more commonly used.